1. Field of the Invention
The present invention relates generally to medical implant communication systems, and in particular to methods for a base station and for an implantable medical device in such systems.
2. Description of the Prior Art
In a medical telemetry system an implantable device such as a pacemaker is monitored regularly by an external programming device. A physician treating the patient can thereby obtain important information, for example in order to evaluate the heart activity of the patient. The physician is also able to make changes to the settings of the implantable device if such need arises. In order to accomplish this bidirectional communication, a radio connection has to be set up between the programming device of the telemetry system and the implantable device.
United States Patent Application Publication No. 2003/0220673 is directed to methods for combating interference occurring in a telemetry system and to enabling multiple programmers to communicate with multiple implantable devices. Some aspects of selecting a channel are also discussed. The programmers may for example dynamically store a table and mark channels used by other programmers and devices as reserved, or they may coordinate their use of the telemetry channels.
However, arranging the programmers to coordinate their use of channels is tedious and requires programs, operating parameters and elaborate algorithms for implementing the methods, which thus increases the overall costs of the medical telemetry system. Further, having a pre-arranged channel on which communication is to be conducted entails a number of drawbacks. For example, the pre-arranged channel may not be the channel that is best suited for communication at the time and this is also a rather non-flexible method.
Further, European Standard ETSI EN 301 839-1 defines characteristics that a medical implant communications system (MICS) has to meet. The available spectrum has to be used as efficiently as possible and the document specifies some requirements that have to be fulfilled. These requirements have to be taken into consideration when designing a MICS system and the devices used within the system.
It would thus be desirable to provide an improved method for establishing a connection between a base station and an implantable medical device of a telemetry system. Further, it would be desirable to provide such method, fulfilling the requirements set by the above-mentioned ETSI standard.